This invention relates to marking or writing elements and is particularly concerned with a "cold-processed" thermoset lead.
For many years the ceramic-type pencil leads, comprising principally graphite and clay that must be processed at temperatures as high as 2,000.degree. F., have been predominant in the pencil industry. (See, e.g., the discussion of the manufacture of such leads in U.S. Pat. No. 3,360,489, assigned to the same assignee as the present invention.) More recently pencil leads employing thermoplastic resin binders have made substantial inroads in the domain of the ceramic leads. Some of the thermoplastic leads have approached parity with the ceramic leads in strength and writing qualities, but prior attempts to produce satisfactory pencil leads with a thermosetting resin system have failed. In general, prior thermoset pencil leads have been deficient in strength and/or writing qualities and have been difficult and expensive to manufacture.